1. Field of the Invention
An embodiment of the present invention relates to the field of patient scanning devices.
2. Discussion
Cardiac scanners provide a non-invasive manner in which to gather information used to aid in the diagnoses of current or possible future health problems associated with a patient's heart. For example, cardiac scanners can employ a Single Photon Emission Computed Tomography (SPECT) scan to generate a detailed image of the patient's heart. In a SPECT scan, a radionuclide is injected intravenously into a patient, and, as the radionuclide is circulated in the blood, the tissues absorb the radionuclide. Then, a detector (camera) is used to scan the portion of the patient that is of interest in the examination, and the detector detects photons of the radionuclide particles, and this information is transferred to a computer that converts this information into cross-sections of the patient and generates a 3-D image of the patient from the cross-sections.
Several dedicated cardiac scanners are available in the marketplace that utilize various detectors and drive systems in order to scan the torso of a patient in order to generate images of the patient's heart. Generally, such dedicated cardiac scanners use one or more detectors to capture multiple images about a certain angular circumferential range of the patient's torso, and these images are combined to form the 3-D image of the patient's heart.
One example of such a cardiac scanner, namely a C.cam™ scanner made by Siemens, is shown in FIGS. 1A and 1B. FIG. 1A is a perspective view of the Siemens scanner 10, and FIG. 1B is a perspective view of the scanner 10 with a patient thereon in a patient scanning position, which is close to horizontal. This scanner 10 includes a camera having two detectors integrated into one housing 12. The motion of the detectors about the patient's torso during scanning is provided by an articulated arm 14 powered about three drive axes. The articulated arm 14 moves the detectors around the patient's body following the contour thereof.
Another example of a cardiac scanner is made by Spectrum Dynamics. FIG. 2 is a cross-sectional, schematic representation of a scanning unit 20 of the Spectrum Dynamics scanner. In this scanner, the scanning unit 20 is moved into position with respect to the patient's body 26 prior to scanning using two drive axes (not shown), and then scanning takes place with a housing 22 of the scanning unit 20 remaining in a stationary position. The scanning unit 20 includes multiple detectors 24 that rotate (or wiggle) back and forth (two positions are depicted for each detector in FIG. 2) in order to scan the patient. Thus, during scanning, the multiple detectors 24 inside the stationary housing 22 wiggle slightly around their own axes scanning the patient's body in a sweeping motion.
Yet another example of a cardiac scanner is made by CardiArc. FIG. 3 is a schematic, perspective view of a detector unit 30 and an oscillating aperture arc 34 of a scanning unit of the CardiArc scanner. This scanner has a half donut shaped enclosure (not shown) that is positioned about the torso of the patient. The detector unit 30 is mounted in a stationary position within the enclosure, and the detector unit 30 has multiple detector boards 32 mounted in a spaced apart relationship to one another along the detector unit 30. The multiple stationary detector boards 32 are arrayed in a 180° arc surrounding the patient's torso. The aperture arc 34 is a thin sheet of lead having spaced apart apertures 36. During scanning, all of the detector boards are active simultaneously, and the aperture arc 34 is rotated slightly back and forth to produce multiple rays sweeping across each of the detector board's field of view, thereby providing an acquisition of data.